NYC-WTC_000208816

NYC 9/11 Public Portal Document

Freon-22 (chlorodifluoromethane); Freon-22 was detected and identified at the WTC site. Observed concentration path lengths of 1-10 parts per million-meter* are consistent with small leak rates of < 10 grams per second. ?? The observed emissions were variable in size, intensity, and location. ?? Many of the observations are consistent with the known locations of the 12 large freon tanks at the WTC site.

Ammonia: Ammonia was detected and identified emanating from the debris piles of both the North and South Towers at approximate concentration levels of 100 parts per million meter. The source of ammonia is unknown but may be a result of the high temperature decomposition of a number of materials in a reducing environment.

Methanol: Methanol was detected and identified, principally from the South Tower. Concentration lengths were measured at approximately 10-100 parts per million meter*.

Toxic carbonyl products: The presence of toxic carbonyl products (e.g., phosgene) has never been detected at even moderate confidence in these analyses.

Additional analysis: Analysis of additional data sets is continuing.

* The concentration path length products (parts per million meter) is the product of the average concentration in a plume above a point on the ground and the depth of the plume. The sensor used in these analyses does not provide a good measure of either of these quantities independently.

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NYC-WTC_000208817